A white light-emitting device comprises a combination of, for example, a blue LED, a fluorescent substance that emits red light under excitation by blue light, and another fluorescent substance that emits green light under excitation by blue light. However, if containing a fluorescent substance that emits yellow light under excitation by blue light, the white light-emitting device can be produced by use of fewer kinds of fluorescent substances. The yellow-light emitting fluorescent substances include Eu-activated orthosilicate phosphors.
Various studies have been made on the use of the yellow-light emitting fluorescent substances, and accordingly demands have been increasing for the fluorescent substances on temperature characteristics, quantum yield and color rendering properties.